Fingerprints and other types of biometric authentication are considered more secure than PIN-based passwords and can eliminate issues such as password theft. Furthermore, biometrics can be more convenient and faster than typing passwords. However, there are some issues with existing fingerprint sensors. For example, the sensor component and its sensing area take up “real estate” on the front face of the mobile device. This limits how much of the front face of the device the display can occupy, and thus limits the overall display and phone dimensions. This can lead to tradeoffs between display size and fingerprint sensor size, but a smaller sensing area may cause user authentication to be less accurate, and lead to more erroneous authentication failures. Additionally, the user experience is interrupted by the authentication process when the user is interacting with applications. For example, to confirm a payment or log into an account, the device must prompt the user to move his or her finger off the touch-screen of the display, touch the fingerprint reader, and then resume the previous task.